This invention relates to a process for producing a high molecular weight condensation polymer.
The weight average molecular weight (Mw) of a condensation polymer is frequently limited by the formation and presence of by-products during the polycondensation reaction. In these types of polycondensation equilibrium reactions, which are driven by the removal of a by-product, e.g. water, alcohol, phenol, etc., removal of the by-product enables the polymer chain end to react further, thus building the molecular weight of the polymer produced. However, methods of removing by-product(s) during the reaction process are difficult and costly due to the increased viscosity of the polymer produced. For example, DE-4,236,039 discloses a method for the production of condensation polymers by circulating the reaction mixture through tubular heat exchangers to remove a majority of the water by-product, further completing the reaction, and removing additional water by-product in a secondary similar stage. This process requires multiple reactors, and water removal stages. Other methods of solving the problem associated with removing unwanted by-products from polycondensation equilibrium reactions include diffusion and solid state polymerization processes. However, these methods incorporate long residence times, which can cause other additional by-products, such as color bodies or gels, to form.
Therefore, there remains a need for a more efficient and rapid process for removing by-product(s) from polycondensation equilibrium reaction mixtures and thus increasing the molecular weight of the condensation polymer produced.